hi! do you mean the default gridlines that comes with excel?
i think you can only get rid of it if you change background color of multiple cells, to do that you will need to tweak the xml representation of the excel to define the colors, to see how this representation should look like check this reference to the Office Open XML spec
no, but you just need to translate the xlsxAddImage to a function call in ejs syntax.
other thing can be that ejs works different with helpers, and since ejs is external extension (not part of core jsreport extensions) maybe it has some bug when working with xlsx recipe, if that is the case we will need an example link in playground that shows the bug